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Bug 1524 - WiFi fragmentation issue

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This commit is contained in:
Daniel Lertpratchya
2012-12-05 14:27:54 -05:00
parent ae21650756
commit 2fcb9b89ff
3 changed files with 63 additions and 13 deletions
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1
RELEASE_NOTES
View File

@@ -40,6 +40,7 @@ Bugs fixed
- bug 1495 - test.py claims test passed when no test was run
- bug 1509 - rttEstimator returns invalid value in presence of errors
- bug 1532 - unimplemented LTE Scheduler methods
- bug 1524 - Fragmentation Threshold equals to Packet Size at MAC Layer (Data + IP + UDP) crash the reception
Known issues
------------

70
src/wifi/model/wifi-remote-station-manager.cc
View File

@@ -165,7 +165,8 @@ WifiRemoteStationManager::GetTypeId (void)
"than this value, as per IEEE Std. 802.11-2007, Section 9.4. "
"This value will not have any effect on some rate control algorithms.",
UintegerValue (2346),
MakeUintegerAccessor (&WifiRemoteStationManager::m_fragmentationThreshold),
MakeUintegerAccessor (&WifiRemoteStationManager::DoSetFragmentationThreshold,
&WifiRemoteStationManager::DoGetFragmentationThreshold),
MakeUintegerChecker<uint32_t> ())
.AddAttribute ("NonUnicastMode", "Wifi mode used for non-unicast transmissions.",
WifiModeValue (),
@@ -239,7 +240,7 @@ WifiRemoteStationManager::GetRtsCtsThreshold (void) const
uint32_t
WifiRemoteStationManager::GetFragmentationThreshold (void) const
{
return m_fragmentationThreshold;
return DoGetFragmentationThreshold ();
}
void
WifiRemoteStationManager::SetMaxSsrc (uint32_t maxSsrc)
@@ -259,7 +260,7 @@ WifiRemoteStationManager::SetRtsCtsThreshold (uint32_t threshold)
void
WifiRemoteStationManager::SetFragmentationThreshold (uint32_t threshold)
{
m_fragmentationThreshold = threshold;
DoSetFragmentationThreshold (threshold);
}
void
@@ -497,10 +498,53 @@ WifiRemoteStationManager::NeedFragmentation (Mac48Address address, const WifiMac
bool normally = (packet->GetSize () + header->GetSize () + WIFI_MAC_FCS_LENGTH) > GetFragmentationThreshold ();
return DoNeedFragmentation (station, packet, normally);
}
uint32_t
WifiRemoteStationManager::GetNFragments (Ptr<const Packet> packet)
void
WifiRemoteStationManager::DoSetFragmentationThreshold (uint32_t threshold)
{
uint32_t nFragments = packet->GetSize () / GetFragmentationThreshold () + 1;
if (threshold < 256)
{
/*
* ASN.1 encoding of the MAC and PHY MIB (256 ... 8000)
*/
NS_LOG_WARN ("Fragmentation threshold should be larger than 256. Setting to 256.");
m_fragmentationThreshold = 256;
}
else
{
/*
* The length of each fragment shall be an even number of octets, except for the last fragment if an MSDU or
* MMPDU, which may be either an even or an odd number of octets.
*/
if (threshold % 2 != 0)
{
NS_LOG_WARN ("Fragmentation threshold should be an even number. Setting to " << threshold - 1);
m_fragmentationThreshold = threshold - 1;
}
else
{
m_fragmentationThreshold = threshold;
}
}
}
uint32_t
WifiRemoteStationManager::DoGetFragmentationThreshold (void) const
{
return m_fragmentationThreshold;
}
uint32_t
WifiRemoteStationManager::GetNFragments (const WifiMacHeader *header, Ptr<const Packet> packet)
{
//The number of bytes a fragment can support is (Threshold - WIFI_HEADER_SIZE - WIFI_FCS).
uint32_t nFragments = (packet->GetSize () / (GetFragmentationThreshold () - header->GetSize () - WIFI_MAC_FCS_LENGTH));
//If the size of the last fragment is not 0.
if ((packet->GetSize () % (GetFragmentationThreshold () - header->GetSize () - WIFI_MAC_FCS_LENGTH)) > 0)
{
nFragments++;
}
return nFragments;
}
@@ -509,19 +553,21 @@ WifiRemoteStationManager::GetFragmentSize (Mac48Address address, const WifiMacHe
Ptr<const Packet> packet, uint32_t fragmentNumber)
{
NS_ASSERT (!address.IsGroup ());
uint32_t nFragment = GetNFragments (packet);
uint32_t nFragment = GetNFragments (header, packet);
if (fragmentNumber >= nFragment)
{
return 0;
}
//Last fragment
if (fragmentNumber == nFragment - 1)
{
uint32_t lastFragmentSize = packet->GetSize () % GetFragmentationThreshold ();
uint32_t lastFragmentSize = packet->GetSize () - (fragmentNumber * (GetFragmentationThreshold () - header->GetSize () - WIFI_MAC_FCS_LENGTH));
return lastFragmentSize;
}
//All fragments but the last, the number of bytes is (Threshold - WIFI_HEADER_SIZE - WIFI_FCS).
else
{
return GetFragmentationThreshold ();
return GetFragmentationThreshold () - header->GetSize () - WIFI_MAC_FCS_LENGTH;
}
}
uint32_t
@@ -529,8 +575,8 @@ WifiRemoteStationManager::GetFragmentOffset (Mac48Address address, const WifiMac
Ptr<const Packet> packet, uint32_t fragmentNumber)
{
NS_ASSERT (!address.IsGroup ());
NS_ASSERT (fragmentNumber < GetNFragments (packet));
uint32_t fragmentOffset = fragmentNumber * GetFragmentationThreshold ();
NS_ASSERT (fragmentNumber < GetNFragments (header, packet));
uint32_t fragmentOffset = fragmentNumber * (GetFragmentationThreshold () - header->GetSize () - WIFI_MAC_FCS_LENGTH);
return fragmentOffset;
}
bool
@@ -538,7 +584,7 @@ WifiRemoteStationManager::IsLastFragment (Mac48Address address, const WifiMacHea
Ptr<const Packet> packet, uint32_t fragmentNumber)
{
NS_ASSERT (!address.IsGroup ());
bool isLast = fragmentNumber == (GetNFragments (packet) - 1);
bool isLast = fragmentNumber == (GetNFragments (header, packet) - 1);
return isLast;
}
WifiMode

5
src/wifi/model/wifi-remote-station-manager.h
View File

@@ -393,7 +393,10 @@ private:
/// Find a remote station by its remote address and TID taken from MAC header
WifiRemoteStation* Lookup (Mac48Address address, const WifiMacHeader *header) const;
WifiMode GetControlAnswerMode (Mac48Address address, WifiMode reqMode);
uint32_t GetNFragments (Ptr<const Packet> packet);
void DoSetFragmentationThreshold (uint32_t threshold);
uint32_t DoGetFragmentationThreshold (void) const;
uint32_t GetNFragments (const WifiMacHeader *header, Ptr<const Packet> packet);
typedef std::vector <WifiRemoteStation *> Stations;
typedef std::vector <WifiRemoteStationState *> StationStates;